Preliminary Analysis of the Cladding Mechanical Behavior of a Nuclear Superheat Boiling Water Reactor

Transcription

1 Int J Advnced Design nd Mnufctuing echnology, Vol. / No. / June Peliminy Anlysis of the Cldding Mechnicl Behvio of Nucle Supehet Boiling Wte Recto Mjid Bhon Deptment of Nucle Engineeing, Science nd Resech bnch, Islmic Ad Univesity, ehn, In. E-mil: mjid_bhn@yhoo.com Gholme Jhnfni* Deptment of Nucle Engineeing, Science nd Resech bnch, Islmic Ad Univesity, ehn, In. E-mil: ejhn@yhoo.com *Coesponding utho Mote Ghib Deptment of Nucle Engineeing, Science nd Resech bnch, Islmic Ad Univesity, ehn, In. E-mil: mghib@yhoo.com Received: 30 Jnuy 08, Revised: 9 Febuy 08, Accepted: 7 My 08 Abstct: In the pesent study, investigtion of mechnicl behviou of the fuel mteil fo nucle supehet Boiling Wte Recto with nnul fuel ods, is cied out. In this design, ech nnul fuel element is cooled intenlly by stem nd extenlly by wte. Fo the fuel mteil, dition embittement nd idition-ssisted stess coosion ccking (IASCC) e the most impotnt issues tht hve to be tken into ccount. Hence, fo, two mteils e consideed. Peliminy theml expnsion nd stess nlysis hve been done fo fesh (begin of cycle) ASBWR (Annul-fuelled Supehet Boiling Wte Recto) fuel element. he pupose of these nlysis is to investigte the stess distibution nd theml expnsion of the in the initil phse of opetion. he esults show tht thee is noticeble diffeence in the xil expnsion between the inne nd oute s. Fo 9 (modified 9C-Mo steel), the mximum xil theml gowth of the inne is. mm, which is bout 9.7 mm moe thn the oute. Fo Inconel 78, the esults e 7.8 mm nd 3.4 mm, espectively. Keywods: Annul fuel, Stin, Stess, Supehet BWR, heml expnsion Refeence: Bhon, M., Jhnfni, Gh., nd Ghib,M., Peliminy Anlysis of the Cldding Mechnicl Behvio of Nucle Supehet Boiling Wte Recto, Int J of Advnced Design nd Mnufctuing echnology, Vol. /No., 08, pp Biogphicl notes: Mjid Bhon eceived his PhD in Nucle Engineeing fom IAU, Science nd Resech Bnch, in 07. His esech inteests include powe plnt technology, Recto theml-hydulic nd sfety nlysis, nd two phse flow. Gholme Jhnfni eceived his PhD in Nucle Powe Plnt fom Univesity of Moscow, in 005. He is cuently Pofesso t the Deptment of Nucle Engineeing, science nd esech bnch Univesity, ehn, In. His cuent esech inteest includes powe plnt technology nd two phse flow. Mote Ghib is Associte Pofesso of Nucle engineeing t the Amikbi Univesity nd IAU, In. He eceived his PhD in Nucle engineeing fom Pensylvni Univesity of USA. 08 IAU, Mjlesi Bnch

2 40 Int J Advnced Design nd Mnufctuing echnology, Vol. / No. / June - 08 INRODUCION A selection of vilble nd pomising mteils fo ecto in-coe components is bsed on thei mechnicl nd nucle popeties, coosion nd ceep fctue esistnce, idition stbility nd mnufctuing fesibility. Pticully fo the fuel mteil in nucle ecto, dition embittement nd iditionssisted stess coosion ccking (IASCC) e the most impotnt issues tht hve to be tken into ccount. Supeheting cn be incopoted in nucle powe plnts by the ddition of eithe nucle o fossil fuelfied supe hete. Nucle supe hetes cn be futhe ctegoied into two types: () the septe o nonintegl nucle supe hete nd (b) the integl nucle supe hete []. he non-integl nucle supe hete is nmely stem-cooled ecto. It only dds supehet to stem nd the stem coolnt is supplied fom othe souces, such s light wte ecto (LWR) o fossil powe plnt. Fo integl nucle supe hete, stem is geneted nd supeheted by using the sme coe. Although the ecto design will be moe complicted, it is believed tht the integl nucle supe hete is moe cost-effective thn the septe one becuse it needs only one coe nd one ecto pessue vessel to poduce supeheted stem. It is essentil to use dvnced mteils fo the in-coe nd out-of-coe stuctues. he in-coe stuctues, such s fuel, e the most citicl components in the pessue vessel, s they e exposed to the highest sevice tempetue, to sevee idition dose, nd to the oxidiing supeheted stem envionment. he desible chcteistics of the in-coe mteils include good mechnicl stength t high tempetues, esistnce to dition dmge nd coosion, low neuton bsoption coss section nd good het tnsfe popeties. In ode to tke dvntge of the bundnt expeience fom tody's light wte ectos, s well s impove the LWR technology, this study evlutes mechnicl behvio of the fuel- design of n integl nucle supe hete cooled by wte nd stem. In this ppe, mechnicl nlysis of supehet BWR fuel in stedy stte conditions is cied out. hough peliminy study, two mteils e consideed to hve the potentil to fulfill the equiements s in-coe nd stuctul mteils in the ASBWR. 0 to 0% stuted stem, continues to flow upwd nd entes the nnul septo nd dye, (Fig. & Fig. ). Annul septos nd stem dyes e locted bove the coe in the ecto vessel. he fuel ssembly contins sixty nnul fuel elements nd one sque wte od in n 8 8 sque y. he stem coolnt fist flows downwd to the 8 centl fuel elements nd entes stem box t the bottom end of the fuel element nd then, the stem coolnt is ediected to the 3 peiphel fuel elements. he view of the stem box nd poposed fuel ssembly e shown in Fig. 3 nd Fig. 4. he min design dt is summied in ble. Fig. Flow configution of Supehet BWR by KO [] MEHODS AND RESULS In ech fuel ssembly fo poposed design by YU-Chi KO [], wte is heted by the oute sufce of the nnul fuel elements nd the stem-wte o two-phse mixtue is fomed though the heting pths (o subchnnels). he two-phse mixtue, composed of bout Fig. A view of poposed fuel ssembly [] 08 IAU, Mjlesi Bnch

3 Int J Advnced Design nd Mnufctuing echnology, Vol. / No. / June ble Supehet BWR design dt Pmetes Unit Vlue Recto heml Powe MW 50 System Pessue b 7.3 Fuel ssembly vege powe MW 6.5 No. of fuel ssembly - 9 Fuel mteil - UO Cldding mteil - 9/Inconel78 Fuel vege enichment % 6-7 Fuel inside dimete mm 0 outside dimete mm 9.6 Height of fuel od m 3 No. of Spces - 7 Pitch of fuel ods mm 3 Assembly oute dimension mm 93.7 Inlet mss flow te kg/s 6.3 Outlet stem tempetue ᴼC Efficiency % 40 he het tnsfe eqution in cylindicl coodinte with boundy conditions e solved with fluid equtions, (Fig.5 & Fig.6). he functions of stem box e collecting the incoming stem coolnt; poviding mixing spce fo the stem coolnt to educe the locl tempetue peking; nd diecting the stem coolnt bck to the peiphel up-flow fuel elements. It includes of the uppe stem box nd the lowe stem box. Fig. 5 Configution of fuel element. Fig. 3 A view of stem box Fig. 6 Boundy conditions in fuel element Fig. 4 Downwd nd upwd egions in fuel ssembly he poposed design, should impove sfety mgins to tht of the existing BWRs including limittion on minimum citicl powe tio, mximum fuel nd tempetue. Futhemoe, it is impotnt to confim tht the dvntges gined in highe theml efficiency must not be lost though depeciting fctos, such s lowe llowble powe density in the supeheting egion o excessively highe nnul fuel fbiction costs. 08 IAU, Mjlesi Bnch

4 4 Int J Advnced Design nd Mnufctuing echnology, Vol. / No. / June - 08 Fo mteil, the fist cndidte is the modified 9C-Mo steel (9). It is feites-mtensitic steel cuently used in fossil powe plnt supe hetes. 9 hs lowe theml expnsion coefficient comped to stinless steel nd hs excellent pefomnce unde 650ᵒC. he potentil of 9 fo nucle pplictions hs been ecently studied. It is consideed s one of the pomising stuctul mteils fo the led-bismuthcooled cceleto diven system (ADS) [3]. In ddition, the fesibility of using 9 s fuel in supeciticl wte ectos is lso unde investigtion [4]. he second cndidte is Inconel 78. It is pecipittionhd enble nickel-chomium lloy contining significnt mounts of ion, niobium, nd molybdenum long with lesse mounts of luminum nd titnium. Inconel 78 combines excellent coosion esistnce nd tensile, ftigue, ceep, nd uptue stength with outstnding weld bility, including esistnce to post weld ccking. It hs stisfctoy pefomnce when opeted between-43 to 300ᵒF. Comped with stinless steel, Inconel 78 hs impoved ductile to bittle tnsition behvio unde idition nd theml ceep fctue esistnce of the duing tnsients. In ddition, Inconel 78 hs been poposed s mteil fo liquid metl nd gs-cooled fst beede ectos [5]. ble Young's modulus of the mteils [6,7] empetue(ᵒc) Young modulus (GP) 9 Inconel ble 3 Line theml expnsion coefficients of the mteils [6,7] Line theml expnsion empetue(ᵒc) coefficient ( 0 6 / K) 9 Inconel Peliminy theml expnsion nd stess nlyses hve been done fo fesh ASBWR fuel element. he pupose of these nlyses is to investigte the stess distibution nd theml expnsion of the in the initil phse of opetion. All ssumptions pplied to the nlysis e listed in ble. Young's modulus nd line theml expnsion coefficients of the mteils e listed in ble nd ble 3, espectively [6,7]. Fig. 7 illusttes the pessue cting on the inne nd oute of the fesh fuel. Fig. 8 shows the foce blnce fo clcultion of the xil stesses. Fig. 7 Illusttion of the pessues cting on Fig. 8 Blnce of the xil foces Stesses cused by pessue cn be expessed s the following equtions [8]. Fo the inne : i ( Pst Pgp) () P P i st gp () 08 IAU, Mjlesi Bnch

5 Stess (MP) Int J Advnced Design nd Mnufctuing echnology, Vol. / No. / June i ( 3 ) Pgp ( 4 ) Pfw (3) ( ) ( ) Fo the oute : o 4 3 ( Pfw Pgp) (4) P P o 3 gp 4 fw (5) 4 3 o ( 3 ) Pgp ( 4 ) Pfw (6) ( ) ( ) 4 3 Whee the supescipts o, i, efe to oute nd inne s espectively; Pst, Pgp nd Pfw efe to stem, gp nd wte pessues, espectively,,, efe to dil, hoop nd xil stesses, espectively. ble 4 summies the clcultion esults. It cn be found tht the inne is subject to tensile hoop stess while the outing is subject to compessive hoop stess t the beginning of cycle. Howeve, fte the fuel bun-up inceses, the fuel intenl pessue will incese considebly due to the elese of fission gs fom the fuel pellets. he plenum pessue will eventully be highe thn the system pessue, nd then the inne nd oute s will be subject to compessive nd tensile stesses, espectively. If the wll of long hollow cylinde is heted nonunifomly though its thickness, its elements would not expnd unifomly nd theml stesses e induced due to this mutul intefeence. Consideing the stuctue s long, hollow cylinde, its theml stesses cn be expessed s [8]: b E [ ( ) d ( ) d] (7) ( ) b b E [ ( ) d ( ) d ( ) ] (8) ( ) b b E [ ( ) d ( )] (9) ( ) b Whee the supescipts efe to theml stesses,, v nd E e theml expnsion, Poisson tio nd Young's modulus, espectively, nd b e inne nd oute dius, espectively. his nlysis ssumes the long cylinde to be xilly unconstined. Fig. 9 shows the pek theml stesses on the stem side (inne). he mximum dil theml stess ( ) is bout.33 MP which is negligible comped to nd. Fig. 0 shows the mximum theml stesses on the wte side (oute) of the. Comped with Fig. 9, the wte side hs slightly highe mximum theml stesses becuse its dil tempetue distibution is less unifom thn tht of the stem side. ble 4 Clcultion esults of the stesses cused by pessue t the beginning of fuel life Inne Oute Fig Fig. 0 σ (MP) σ θ(mp) σ (MP) Pek theml stesses on the stem side (inne) Axil theml stess Hoop theml stess Rdil theml stess Rdil Distnce(mm) Pek theml stesses on the wte side (oute) Duing plnt opetion, defoms gdully due to pessue, theml expnsion nd idition effects etc. 08 IAU, Mjlesi Bnch

6 44 Int J Advnced Design nd Mnufctuing echnology, Vol. / No. / June - 08 In this section, defomtion of fesh fuel cused by pessue nd theml expnsion is evluted. Stins cused by pessue nd theml expnsion cn be expessed s [8]: [ ( )] d E (0) 0 [ ( )] d E () [ ( )] E 0 0 d () Whee,, e dil, hoop nd xil stins, espectively; t efeence tempetue (0ᵒC). In this evlution, the mteil is ssumed to expnd isotopiclly, theefoe = =, =. ble 5 summies the clcultion esults of stins, dil displcement, nd xil nd dil gowths due to pessue nd theml expnsion fo the hot chnnel. he stem down-flowing nd up-flow chnnels hve diffeent xil gowths of the inne since stem tempetue is highe in the up-flow chnnels. Fo the xil gowth of the oute, the esults between the stem down-flow nd up-flow chnnels e bout the sme. Although the dil stin is bout the sme mgnitude s the xil stin, the dil gowth in is vey smll due to the thin thickness. ble 5 Results of stin clcultion of the bse cse (9 ) Inne Oute Inne Oute Axil stin Axil gowth (mm) Rdil stin Rdil gowth (mm) Hoop stin In ddition, it cn be seen fom ble 5 tht thee is noticeble diffeence in xil gowth between the inne nd oute s. Fo the stem up-flow chnnel, the xil gowth of the inne is.4 mm nd is.5 mm fo the oute. he diffeence is bout cm. On the othe hnd, the diffeence in xil gowth between the inne nd oute s of the stem down-flow chnnel is only 0.4 cm. ble 6 summies the clcultion esults of xil gowth due to pessue nd theml expnsion. Results of the vege nd hot chnnels e lso comped. It is found tht the esults of xil gowth between the vege nd hot chnnels e ppoximtely within diffeence of mm. Futhemoe, Inconel 78 hs lge ovell xil gowth nd lge diffeence in xil gowth between the inne nd oute s due to its highe theml expnsion coefficient. Given the powe density of 50 kw/l, fo Inconel 78 the mximum xil gowth is 7.7 mm while fo 9 it is. mm. ble 6 Clcultion Results of xil gowth due to pessue nd theml expnsion 9 Inconel78 Axil gowth(mm) Inne Stem down- Oute flow. 4.5 Avege chnnel Inne Stem upflow Oute Inne Stem down- Oute flow Hot chnnel Inne Stem.7.77 upflow Oute ble 7 shows the esults of xil gowth due to pessue nd theml expnsion with vious powe densities. ble 7 Impct of powe density on the xil gowth Powe density(kw/l) 9 Inconel78 9 Inconel78 Mximum xil gowth(mm) Diffeence of xil gowth between inne nd oute s(mm) IAU, Mjlesi Bnch

7 Int J Advnced Design nd Mnufctuing echnology, Vol. / No. / June As shown in ble 7, s the powe density inceses, the ovell xil gowth nd the diffeence in xil gowth between the inne nd oute s lso incese. he ovell xil gowth is expected to be ccommodted by the sping ends. he diffeence in xil gowth between the inne nd oute s is expected to be compensted by bellows. 3 CONCLUSION In this study, Peliminy nlysis of the theml expnsion nd stess distibution hve been done fo the fesh ASBWR fuel. he esults indicte tht thee is noticeble diffeence in the xil expnsion between the inne nd oute s. Fo 9, the mximum xil theml gowth of the inne is. mm, which is bout 9.7 mm moe thn the oute. Fo Inconel 78, the esults e 7.7 mm nd 3.4 mm, espectively. he ovell xil expnsion is expected to be ccommodted by spings t the fuel element uppe end. he uneven xil expnsion between the inne nd oute s is expected to be compensted by bellows. Futhe studies e needed to investigte the long tem fuel pefomnce nd the elibility of the poposed end spings nd bellows. REFERENCES [] Novick, M., et l., Developments in Nucle Supehet, Poceedings of the hid Intentionl Confeence on the Peceful Uses of Atomic Enegy, Genev, Aug. 3, Sep. 9, 964. [] Chih Ko, Yu., Conceptul Design of n Annul-Fueled Supehet Boiling Wte Recto, MI Ph.D hesis, Jun. 00. [3] Spundjiev, D., Al Moui, A., nd Vn Dyck, S., A Study of the Neuton Idition Effects on the Susceptibility to Embittlement of A36L nd 9 Steels in Led-Bismuth Eutectic, Jounl of Nucle Mteils, Vol. 356, No. -3, Sep. 006, pp [4] Chen,., Sidhn, K., nd Allen,., Coosion Behvio ffeitic-mtensitic Steel 9 in Supeciticl Wte, Coosion Science, Vol. 48, No. 9, 006, pp [5] Fole, R., Gs-Cooled Fst Beede Recto Designs with Advnced Fuel nd Cldding, Nucle Engineeing nd Design, Vol. 40, No., Jn. 977, pp [6] Incone 78 Popeties, On-line Resouce, Avilble fom Wold Wide Web: [7] Ashfi Nik, M., Dec. hemo Hydulic Optimition of the EURISOL DS get, No., M , 006. [8] Hvey, J. F., heoy nd Design of Pessue Vessels, Spinge, Sep IAU, Mjlesi Bnch